2IFJ

Lys6 deamidated variant of ImI conotoxin

Summary for 2IFJ

• Entry DOI: 10.2210/pdb2ifj/pdb
• Related: 2IFI 2IFZ 2IGU 2IH6 2IH7
• Descriptor: Alpha-conotoxin ImI (1 entity in total)
• Functional Keywords: conotoxin, disulfide linkages, ribbon conformation, toxin
• Total number of polymer chains: 1
• Total formula weight: 1390.66

Authors

Kini, R.M.,Kang, T.S. (deposition date: 2006-09-21, release date: 2007-08-14, Last modification date: 2022-03-09)

Primary citation

Kang, T.S.,Talley, T.T.,Jois, S.D.,Taylor, P.,Kini, R.M.
Protein folding determinants: structural features determining alternative disulfide pairing in alpha- and chi/lambda-conotoxins
Biochemistry, 46:3338-3355, 2007

PubMed Abstract: Alpha-conotoxins isolated from Conus venoms contain 11-19 residues and preferentially fold into the globular conformation that possesses a specific disulfide pairing pattern (C1-3, C2-4). We and others isolated a new family of chi-conotoxins (also called lambda conotoxins) with the conserved cysteine framework of alpha-conotoxins but with alternative disulfide pairing (C1-4, C2-3) resulting in the ribbon conformation. In both families, disulfide pairing and hence folding are important for their biological potency. By comparing the structural differences, we identified potential structural determinants responsible for the folding tendencies of these conotoxins. We examined the role of conserved proline in the first intercysteine loop and the conserved C-terminal amide on folding patterns of synthetic analogues of ImI conotoxin by comparing the isoforms with the regiospecifically synthesized conformers. Deamidation at the C-terminus and substitution of proline in the first intercysteine loop switch the folding pattern from the globular form of alpha-conotoxins to the ribbon form of chi/lambda-conotoxins. The findings are corroborated by reciprocal folding of CMrVIA chi/lambda-conotoxins. Substitution of Lys-6 from the first intercysteine loop of CMrVIA conotoxin with proline, as well as the inclusion of an amidated C-terminal shifted the folding preference of CMrVIA conotoxin from its native ribbon conformation toward the globular conformation. Binding assays of ImI conotoxin analogues with Aplysia and Bulinus acetylcholine binding protein indicate that both these substitutions and their consequent conformational change substantially impact the binding affinity of ImI conotoxin. These results strongly indicate that the first intercysteine loop proline and C-terminal amidation act as conformational switches in alpha- and chi/lambda-conotoxins.

PubMed: 17315952
DOI: 10.1021/bi061969o

Experimental method

SOLUTION NMR